What is a residual current circuit breaker with over current protection?

What is a residual current circuit breaker with over current protection?


Electrical safety is paramount in any residential or commercial setting. To safeguard against electrical faults and ensure the well-being of individuals and property, various protective devices are installed in electrical systems. One such essential device is the residual current circuit breaker with over current protection (RCBO). In this article, we will delve into the concept and functionality of RCBOs, exploring their purpose, operation, and significance in electrical installations.

Understanding Residual Current Circuit Breakers (RCCBs): 

Residual current circuit breakers, commonly known as RCCBs, are devices designed to detect and protect against electrical faults, particularly those involving leakage or residual currents. These currents can occur due to faulty wiring, insulation breakdown, or direct contact with live parts. RCCBs monitor the difference between the current flowing into and out of an electrical circuit and disconnect the power supply when an imbalance is detected.

How does an RCCB work? RCCBs operate based on the principle of differential current sensing. They continuously monitor the electrical current entering and leaving a circuit. If a leakage current, resulting from a fault or electrical shock, is detected, the RCCB rapidly trips and cuts off the power supply. By doing so, it helps prevent electric shock and reduce the risk of fire caused by insulation failures or short circuits.

Understanding Over Current Protection: 

Over current refers to excessive current flowing through an electrical circuit beyond its rated capacity. It can occur due to various reasons such as equipment malfunction, short circuits, or overload conditions. Over current protection is vital to safeguard electrical systems and prevent damage to equipment, wiring, and potential fire hazards.

Residual Current Circuit Breaker with Over Current Protection (RCBO): 

An RCBO is a combination device that integrates the functionalities of both an RCCB and an over current protection device, typically a miniature circuit breaker (MCB). It provides dual protection by detecting and responding to both residual currents and over current conditions. In simpler terms, an RCBO is capable of disconnecting the power supply in the event of both leakage currents and excessive current flow.

Features and Benefits of RCBOs: 

RCBOs offer several key features and benefits that contribute to enhanced electrical safety and system reliability. Some notable advantages include adjustable sensitivity, which allows customization based on specific application requirements, and the ability to provide selective tripping, isolating only the affected circuit while leaving the rest of the installation operational. Additionally, RCBOs occupy less space compared to separate RCCBs and MCBs, simplifying installation and reducing clutter within electrical panels.

Applications of RCBOs: 

RCBOs find application in various settings, including residential, commercial, and industrial environments. In residential buildings, RCBOs are commonly installed in distribution boards to protect circuits connected to lighting, power outlets, and critical appliances. In commercial and industrial settings, where electrical loads are typically higher, RCBOs are used to safeguard specific circuits or equipment that require additional protection.

Considerations for RCBO Selection and Installation: 

When selecting and installing RCBOs, several factors must be taken into account. These include determining the appropriate current rating based on the load requirements, ensuring compatibility with the electrical system and other protective devices, and following manufacturer guidelines and electrical codes during installation. Engaging a qualified electrician is highly recommended to ensure proper selection, installation, and adherence to safety standards.


In conclusion, a residual current circuit breaker with over current protection (RCBO) is a crucial component in electrical systems, providing both residual current protection and over current protection in a single device. Its ability to detect and respond to leakage currents and excessive current flow contributes significantly to electrical safety, reducing the risk of electric shock, fire hazards, and equipment damage. RCBOs find applications in various residential, commercial, and industrial settings, and

their selection and installation should be carried out diligently to ensure optimal performance and compliance with safety regulations. By incorporating RCBOs into electrical installations, we can create safer environments and protect lives and property from electrical faults.

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